1. Field of the Invention
The present invention relates to a cooling system for cooling coolant which circulates through and cools a fuel cell and, more specifically, to a cooling system provided with a prevention system for preventing degradation of the coolant and a method thereof.
2. Description of the Related Art
Fuel cells are clean energy power source and application of the fuel cells to batteries for electric vehicles is now diligently being developed. For example, a fuel cell system of apolyelectrolyte type has been proposed. The fuel cell system is configured to protonate hydrogen in the fuel cell stack as a fuel by means of a protonating catalyst supported by the polyelectrolyte and produce reaction of oxygen existing on the other side of the polyelectrolyte thereupon so as to generate electric power. Namely, the fuel cell system is a kind of power generators utilizing electrochemical reaction.
The fuel cell system produces heat accompanying the reaction so that a temperature thereof tends to rise though there is a proper temperature range. Thereby the fuel cell system is necessarily provided with a cooling system for circulating coolant having a predetermined temperature (about 65 through 70 degree C. for example) through the fuel cell system so as to regulate a temperature of the fuel cell system in the proper temperature range (about 80 through 85 degree C. for example).
The coolant may have certain conductivity for effective action of the fuel cell system, however, excessive conductivity leads to an electric leak via the coolant. Such a situation is undesirable to the fuel cell system. For reducing the conductivity, pure water is conventionally applied to the coolant. Recently, for prevention of freezing in a case of low temperature, utilization of a mixed solution containing glycol is proposed. 50% mixed solution in which ethylene glycol and pure water are evenly mixed (“EG50” hereinafter) can be exemplified as the mixed solution. A related art is disclosed in Japanese Patent Application Laid-open No. 2001-167782.